Low paydays in the first trimester of 2019 have prompted scammers in sextortion email business to switch to new tricks. The scammers resorted to some simple tricks in an attempt to get their messages past the spam filters. By embedding images of the message in the email body, the anti-spam protection mechanism has little information to assess. In more recent campaigns, the scammers play the social engineering card once again. To convince the victim that the blackmail is real, the messages purport to deliver video proof of the act in a ZIP file.
Source: https://www.bleepingcomputer.com/news/security/sextortion-scammers-change-tactics-to-bypass-spam-protection/